1. Technical Field
The invention relates to an image forming method, image forming apparatus and a processing cartridge and an electrophotographic photoreceptor to be employed thereto, which are used for a copying machine, a laser beam printer and a facsimile machine.
2. Related Art
The electrophotographic photoreceptor is usually manufactured by immersing a cylindrical electroconductive support into a coating liquid such as a photosensitive layer coating liquid, an intermediate layer coating liquid and a surface protective layer coating liquid to form a coated layer. In such the case, the coated layer is entirely formed on the surface of the cylindrical electroconductive support since the support is immersed in the coating liquid. When the photoreceptor drum entirely coated with the layer is installed in an electrophotographic apparatus, the coated layer is occasionally peeled off by contacting to parts such as a roller to be touched to a developing device, and the photoreceptor drum cannot be utilized as the contacting point for grounding. Consequently, it is preferable to remove the coated layer adhered at the both end portions of the photoreceptor drum.
As the method for removing the coated layer, methods have been known such as the method described in Japanese Patent Publication Open to Public Inspection, hereinafter referred to as Japanese Patent O.P.I. Publication, No. 63-311357 in which the end portion of the photoreceptor drum is immersed in an solvent and vibrated by ultrasonic wave, the method described in Japanese Patent O.P.I. Publication Nos. 3-60782, 4-141663, 5-142789, 10-207084, 11-184100 and 11-194509 in which the coated layer is scoured off by a brush, and the method employing a tape. The following methods have been known, for example, the method described in Japanese Patent O.P.I. Publication No. 4-65376 in which a tape composed of heat-bonded type nonwoven fabric is successively let out and then a solvent is supplied to the tape, and the tape is contacted to the photoreceptor drum to remove the photosensitive layer the method in which a tape impregnated with a solvent is let out and the tape is contacted to the photoreceptor drum to remove the coated layer, and the method using a nonwoven fabric having uneven surface on one side described in Japanese Patent O.P.I. Publication No. 9-281725.
In any method, however, problems occur such as that the coated layer near the end portion of the photoreceptor where the coated layer is removed is tends to be peeled off, and the toner is accumulated at the end portion of the photoreceptor so as to cause insufficient cleaning and contamination of interior of the apparatus by the toner. As a result of that the durability of the photoreceptor drum and the cleaning member is extremely degraded. Consequently, it is demanded that the shape of the coated layer is developed which does not cause such the problems.
Recently, an organic photoreceptor containing an organic photo-electroconductive substance is most widely employed as the photoreceptor to be used in the image forming apparatus.
The organic photoreceptor is superior to another photoreceptor in that the material capable of corresponding to various exposure light source from visual to infrared rays can be easily developed, the material causing no environmental pollution can be selected and the production cost is low. However, the mechanical strength of the organic photoreceptor is low. Therefore, it has a drawback that the degradation of the photoreceptor surface and the occurrence of damages ten to occur.
Moreover, the toner remained on the photoreceptor after the transfer of the toner image to the image receiving material is difficultly removed since the contact energy of the organic photoreceptor with the toner visualizing the static latent image is large. Accordingly, various problems are raised on the cleaning of the photoreceptor surface.
On the other hand, the image formation by a digital system becomes to the main stream of the electrophotographic image formation accompanied with the progress of the digital technology. The image formation method according to the digital system is based on the visualization of a fine dot image such as 400 dpi (number of dot per inch or 2.54 cm). A high quality imaging technology capable of conscientiously visualizing such the fine dot image is required.
As an important means of the high quality imaging technology, reducing of a fine particle size of the toner, unifying the size and the shape of the toner particle are attempt, and the electrophotographic developer and an image forming method employing a polymerized toner are proposed. The toner having uniform size and shape can be obtained by the polymerization since such the toner particle is prepared by polymerizing a monomer dispersed in an aqueous medium. Such the powder system, however, has complicated physical properties and strong coagulating force even though high sharpness and image quality can be obtained. Consequently, problems such as formation of unevenness of the halftone image and black spots caused by the adhesion of the toner to the photoreceptor or the coagulation of the toner itself and insufficient cleaning such as toner filming and turn off of the cleaning blade tend to occur.
The importance of the fine particle toner is increasingly raised for forming a high quality image in the recent stream of the digitization. Moreover, the toner recycle system for reusing the toner recovered from the photoreceptor by cleaning is advantageous from the viewpoints of the resource saving, pollution prevention and cost saving of image formation.
However, when the fine particle toner is employed in an usual image forming method, various image defects such as coagulation of the toner at the edge portion of the photoreceptor, scattering of the toner caused by the coagulation and peeling of the photoreceptive layer at the edge portion of the photoreceptor caused by the strong stress on the occasion of the cleaning are formed in a period of prolonged development. Such the defects are become considerably when the toner recycle system is applied.
The relation of the shape of the edge of photoreceptive layer and the size distribution of the toner particles not causing the above problems is required. Therefore, an electrophotographic image forming method, image forming apparatus, a processing cartridge and an electrophotographic photoreceptor to be used thereto are demanded, by which the coated layer is not peeled off, the toner is not accumulated and the image defects such as black spot caused by scatter of the powdered coated layer and the toner particle are not formed.